by Nancy Armour, USA TODAY Sports

by Nancy Armour, USA TODAY Sports

When a neck injury forced Peyton Manning to sit out the 2011 season, Tom Brady was one of the people who missed him most.

Never mind that the quarterbacks are rivals. Or that one has sometimes blocked the other from reaching the goal that drives them both, as will happen Sunday when the Denver Broncos and New England Patriots play for the AFC Championship.

Brady and Manning have become forever intertwined by more than a decade of wins and records. They are accidental touchstones, each one's accomplishments defining the other's career as much as his own.

"They have great respect for each other," said Brady's father, Tom Sr. "They understand each other as well as anyone can understand.

"It's pretty special when you have that kind of a relationship. You want to beat the heck out of each other. But you have great respect for one another."

"I think you can have that good competition when you're playing, admire and respect each other," Bradshaw, the Pittsburgh Steelers Hall of Famer and current FOX NFL analyst, said. "Now, we can't compete against each other, but we can respect each other and like one another."

Look at the greatest names across sports, and odds are there was a rival who pushed him to be better, to go further, to refuse to settle for mere success when greatness was within reach. Nicklaus and Palmer. Ali and Frazier. Magic and Bird.

It's tougher to find those iconic rivalries in the NFL, simply because of the dynamics of the game. Players at the same position don't face each other head-to-head, and a quarterback-linebacker rivalry, or a wide receiver vs. a cornerback, just doesn't have the same pizzazz.

"There was never really one. The teams we went against, the quarterbacks changed," Hall of Famer Joe Montana told USA TODAY Sports, referring to when he played for the San Francisco 49ers. "Probably the biggest one was with the (New York) Giants and Phil Simms. ... (But) it never seemed like it was about us, going head to head. You don't look at it like that."

There are those precious rare instances, however, when timing and talent align, and it inspires everyone - including the guy on the opposing sideline - to elevate his game.

"I've been around the game long enough to know that Brady doesn't play Manning and so on. But that duo, they have to match each other," said longtime NFL analyst John Madden, who, as coach of the Oakland Raiders, had a front-row seat for Ken Stabler's epic matchups against Bradshaw's Steelers.

"Both teams know that the other can score a lot of points," Madden told USA TODAY Sports. "You're not going to play Peyton Manning and then not score a lot of points. And you're not going to play Tom Brady and not score a lot of points.

"So they go in against each other and they become very aggressive."

Bradshaw gets best of Staubach

The Raiders and Steelers faced each other in the playoffs every season from 1972-76, with the AFC title at stake in their last three meetings.

In contrast, Hall of Fame quarterbacks Bradshaw and Staubach only played a handful of times because their Steelers and Dallas Cowboys were in different conferences. But they were the premier quarterbacks of their generation, leaders of teams that were the best thing going in the NFL in the 1970s, and that alone would have been enough to create a rivalry.

"We got in the Super Bowls five times in the '70s. I was quarterback for four of them. We were 2-2, and I wish we were 4-0," Staubach told USA TODAY Sports. "And Terry never lets me forget he was 4-0."

That the Super Bowls in which the two faced each other were among the best ever only added to their shared legacy.

Pittsburgh won both times against the Cowboys, but by a total of just eight points. And while Staubach's most vivid memories are of Pittsburgh's "Steel Curtain" defense - "(Jack) Lambert was a mean son of a gun" - he is quick to give Bradshaw his due.

"Bradshaw just made plays when he had to," Staubach said. "He made big plays."

Rules changes spotlight quarterbacks

Montana and Simms were considered quasi-rivals. The Buffalo Bills' Jim Kelly and the Miami Dolphins' Dan Marino are often mentioned in the same breath. But the closest the NFL came to a truly great rivalry in the years between Bradshaw-Staubach and Brady-Manning was that of Dallas' Aikman and San Francisco's Young.

The Cowboys and 49ers were the class of the NFL in the early 1990s, with the NFC Championship Game serving as the de facto Super Bowl. The teams met in the NFC title game from 1993-95, with the winner going on to victory in the Super Bowl each time.

Much like Brady and Manning, Aikman and Young were charismatic, as appealing off the field as they were on.

But those were different times.

Rules have since changed in an effort to give quarterbacks and receivers more protection. As a byproduct, it has helped usher in the golden era of offense.

Offenses were already beginning to open up. But with more time to throw, quarterbacks are more prolific. Look at the list of highest single-season passing yardage, and all but two of the top 12 spots is occupied by a current player.

At the top of the list? Manning, whose 5,477 yards passing this season was a yard more than the mark set in 2011 by Drew Brees of the New Orleans Saints.

"The rules were different," Staubach said. "I think my last year, '79 or '78, was when you're not supposed to hit receivers past five yards. Before, you could hit them all over the field until the ball was in the air. So we didn't throw as much; they really intentionally opened the passing game.

"The most I ever threw it in one game was 49 times, and that was because we were behind. Usually it was around 25," Staubach added. "I'd love to be able to throw the ball 50 times."

Frequency of games make rivalry

As the passing game has taken center stage, so have the guys running it. Before Adrian Peterson snapped the streak last season, a quarterback had won MVP five consecutive years, and in nine of the previous 11.

Only once since the award began in 1957 - 1966-70 - had quarterbacks won five in a row.

Add the increase in endorsement opportunities and proliferation of the media - new and traditional - and the Brady-Manning rivalry has drawn a spotlight like no other.

"This is the greatest quarterback rivalry in the history of football," Simms, who will call Sunday's game for CBS, told USA TODAY Sports. "Bradshaw and Staubach had it there for a while, but nothing as sustained and long and compelling as this one.

"Not even close."

It helps, of course, that Brady and Manning have played each other so often. Sunday's game will be their 15th meeting since 2001, and fourth in the playoffs. It's the fifth time they will play each other twice in the same season.

"I don't know if there ever will be another rivalry, or has been another rivalry, when looking at the numbers that I've seen, with Brady and Manning," says two-time Super Bowl-winning quarterback John Elway, now Manning's boss. "There wasn't, as far as I was concerned in my career, a rivalry that I got to see on the field as much as those guys got to see each other."

But the frequency of Brady's and Manning's meetings has meant inevitable - and often unfavorable - comparisons.

Brady has gotten the better of Manning in their matchups, winning 10 of the 14 games, including New England's comeback from 24 points down to stun the Broncos 34-31 in overtime in November. Manning has more MVPs (four), but Brady has more Super Bowl titles (three).

"I just think that they're two of the very best ever," Brady Sr. said. "And to be able to enjoy that. ... Tommy has even said at different times, 'It's too bad people have to compare us instead of just appreciating our different styles.' "

Said Bill Polian, who drafted Manning first overall when he was general manager of the Indianapolis Colts: "The rivalry itself over time has grown and taken on almost mythical proportions."

But the players involved recognize it for what it is. Both insist the importance of this game - and all the others - is because of the teams playing and what's at stake, not a personal matchup. (Manning says the same thing when he plays little brother Eli and the Giants.)

Like the great rivals of old, however, Brady and Manning appreciate the role the other has played in his career.

Montana mentioned reminiscing with Simms. When Bradshaw lived in Dallas, he and Staubach's paths would cross "quite a bit," Staubach said. And Bradshaw recalled missing the start of the second half of the Pro Bowl one year because he was catching up with former San Diego Charger Dan Fouts, another member of that era's quarterback fraternity.

Although Brady and Manning don't make a show of it, they have become friends over the years, and those closest to them expect that bond could get even stronger when their playing days are done.

"At the end of the day, they're friends now. And I'm sure they'll be better friends in the future," the elder Brady said. "So when they're grandfathers and great grandfathers, they'll appreciate even more what a great ride it has been."